Melissa Rivers has retained a high-profile personal injury law firm to investigate the death of her mother, Joan Rivers, who died Sept. 4, at 81 following a medical procedure at Yorkville Endoscopy, according to reports.

"In order to fully determine all of the facts and circumstances surrounding the death of Joan Rivers we confirm that our firm has been engaged by Melissa Rivers and her family," Ben Rubinowitz, the managing partner of Gair, Gair, Conason, Steigman, Mackauf, Bloom & Rubinowitz told numerous news outlets in a statement Tuesday. .

TMZ reported that lawyers were sending letters Tuesdayto various people involved in the medical procedure telling them not to destroy any records or phone logs involving the Rivers case..

The Office of the Chief Medical Examiner determined earlier this month that Rivers died after her brain became deprived of oxygen during a "laryngoscopy and upper gastrointestinal endoscopy with propofol sedation."

A message to the firm requesting comment was not returned by press time.(Sheila Anne Feeney)